Polyesters represent a commercially important class of polymers. One route to polyesters is via ring-opening polymerization of cyclic esters. For example, ε-caprolactone can by polymerized to polycaprolactone, which is widely used as a biocompatible material for the fabrication of implantable devices. However, known ring-opening polymerization methods typically produce polyesters having relatively low molecular weights. For example, existing polycaprolactones typically have number average molecular weights substantially less than 100,000 atomic mass units. This molecular weight limitation is manifested as a limitation on the mechanical properties of the polymers (including storage modulus, loss modulus, Young's modulus, tensile elongation at break, and melt viscosity), which in turn limits the uses of the polymers. There is therefore a need for improved ring-opening polymerization methods that produce polyesters having higher molecular weights. There is also a need for methods of expediting the breakdown of polymers comprising ester linkages.